Diacetyl, like other alpha-dicarbonyl compounds, is reportedly cytotoxic and genotoxic. A food and cigarette contaminant, it is related with alcohol hepatotoxicity and lung disease. Peroxynitrite is a potent oxidant formed in vivo by the diffusion-controlled reaction of the superoxide radical anion with nitric oxide, which is able to form adducts with carbon dioxide and carbonyl compounds. Here, we investigate the nucleophilic addition of peroxynitrite to diacetyl forming acetyl radicals, whose reaction with molecular oxygen leads to acetate. Peroxynitrite is shown to react with diacetyl in phosphate buffer (bell-shaped pH profile with maximum at 7.2) at a very high rate constant ( k 2 = 1.0 x 10 (4) M (-1) s (-1)) when compared with monocarbonyl substrates ( k 2 < 10 (3) M (-1) s (-1)). Phosphate ions (100-500 mM) do not affect the rate of spontaneous peroxynitrite decay, but the H 2PO 4 (-) anion catalyzes the nucleophilic addition of the peroxynitrite anion to diacetyl. The intermediacy of acetyl radicals is suggested by a three-line spectrum ( a N = a H = 0.83 mT) obtained by EPR spin trapping of the reaction mixture with 2-methyl-2-nitrosopropane. The peroxynitrite reaction is accompanied by concentration-dependent oxygen uptake. Stoichiometric amounts of acetate from millimolar amounts of peroxynitrite and diacetyl were obtained under nonlimiting conditions of dissolved oxygen. In the presence of either l-histidine or 2'-deoxyguanosine, the peroxynitrite/diacetyl system afforded the corresponding acetylated molecules identified by HPLC-MS ( n ). These studies provide evidence that the peroxynitrite/diacetyl reaction yields acetyl radicals and raise the hypothesis that protein and DNA nonenzymatic acetylation may occur in cells and be implicated in aging and metabolic disorders in which oxygen and nitrogen reactive species are putatively involved.

BACKGROUND: The quality and power of each odorous volatile present in the headspace of unifloral honey velame branco (Croton heliotropiifolius Kunth) prepared by stingless uruçu (Melipona scutellaris Latrelle) were evaluated using the gas chromatography-olfactometry Osme technique. Five trained panellists evaluated the sensory chromatographic effluent in three replications, and the results were integrated by SCDTI software. RESULTS:Of the 42 compounds identified in the chromatogram, 17 odorous stimuli were detected by the sensory panel. Among these compounds, the most odoriferous impacts were pentanoate acetate 'ripe fruit', safranal green, medicinal plant and methyl eugenol 'clove, tea'. The furaneol compounds, hotrienol and benzaldehyde showed aroma notes associated with honey. CONCLUSION: These results are important since, in addition to revealing the presence of compounds that are not identified by other analytical methods, they can also assist in the verification of monofloral honeys compliance.

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